Water disinfectant levels likely to be increased next summer

By MARK HAYWARDNew Hampshire Union LeaderOctober 08. 2013 10:23PMMANCHESTER — Manchester Water Works plans to increase disinfectant levels to its drinking water next summer, hoping to avoid a repeat of this summer’s problems with coliform bacteria, the Water Works director said.

Confronted with an outbreak of the harmless bacteria, Water Works officials abandoned the use of the safer disinfectant, chloramine, and added chlorine to the water.

Doing so, however, posed health and water quality risks of its own. Chlorine has a noticeable taste and smell. And when combined with organic material, chlorine forms chemicals that have been linked to bladder cancer, said David Paris, director of Manchester Water Works.

“This is a risk-risk trade off they talk about in public health,” he said.

Since 2006, Manchester Water Works has used chloramine, a compound of chlorine and ammonia, as its secondary disinfectant.

He said he knows of no established studies that have implicated chloramine in any cancer.

“From what we know, chloramine is a far safer choice,” Paris said. But chlorine is a better disinfectant, he said.Chlorine levels in the drinking water were about 2.5 parts per million this summer, Paris said. However, the level should have been 10 to 20 percent higher to curtail the bacteria, he said.

“Retrospectively, we could have put more chlorine in the water,” he said. “Would it have solved the problem? Who knows?”

Paris said he will likely never know what caused the higher bacteria levels, which were found in 26 of 154 samples taken in July. But he believes a sudden hot spell heated the water at Lake Massabesic, which made ideal growing conditions for the bacteria.